Conventional safety arrangements for motor vehicles incorporate a safety-belt and an air-bag to restrain an occupant during a crash situation. The main aim of such conventional safety arrangements is to absorb the kinetic energy of an occupant, when the occupant moves relative to the vehicle as a consequence of inertia or momentum during a crash situation, to prevent the occupant from hitting a solid part of the vehicle. In this way the risk of injury may be reduced. If the kinetic energy of a vehicle occupant can be successfully dissipated, this may prevent the occupant from striking part of the vehicle at speed and possibly facing injury.
The kinetic energy of a vehicle occupant that is to be absorbed is dependent upon the weight of the occupant and the speed at which the occupant moves relative to the vehicle, as the vehicle is decelerated. It is important for a safety arrangement to absorb all of the kinetic energy of a vehicle occupant during a crash situation, so that risk of injury to the occupant may be minimized. It is also important that the safety arrangement does not restrain a seat occupant excessively during an accident situation, as this may itself injure the seat occupant.
Therefore, for a safety arrangement which incorporates a safety-belt and an air-bag, it would be ideal for the total energy which is absorbed by the combination of the safety-belt and the air-bag in any crash situation to be matched to the kinetic energy of an occupant in the crash situation.
The present invention seeks to provide an improved safety arrangement.